Bombardier(WASHINGTON) -- The U.S. Commerce Department placed big tariffs on imports of Canada's Bombardier C Series aircraft on Wednesday, saying exporters of the aircraft were receiving large subsidies.

"The U.S. values its relationships with Canada, but even our closest allies must play by the rules," Commerce Secretary Wilber Ross said in a statement. "The subsidization of goods by foreign governments is something that the Trump administration takes very seriously, and we will continue to evaluate and verify the accuracy of this preliminary determination."

Accusations of the subsidies were leveled by U.S. airplane maker Boeing.

The Commerce Department notes that the aircraft subject to the investigation had not yet been imported to the U.S., but that a press release from last year valued an order placed by one U.S. airline at over $5 billion.

Canada has expressed disappointment with the decision, with Minister of Foreign Affairs Chrystia Freeland calling it a move "aimed at eliminating Bombardier's C Series aircraft from the U.S. market."

The Canada-based company called the size of the tariff "absurd and divorced from the reality about the financing of multibillion-dollar aircraft programs."

Even United Kingdom Prime Minister Theresa May weighed in, saying she was "bitterly disappointed" by the U.S. decision. The British government said the action could jeopardize Boeing contracts with the U.K. Ministry of Defense. That, in part, because Bombardier receives funding from the U.K. government, and the company employs thousands at a plant in Northern Ireland.